Apparatus for producing incremental movement, particularly for moving a print hammer module parallel to a print line

ABSTRACT

Apparatus within a printer for incrementally moving a hammer module parallel to a line on which characters are being printed. The hammer module is carried across the paper by a coil which moves within a track extending parallel to the print line and formed by parts of pole pieces arranged to provide magnetic fields spaced along and extending across the track in alternating opposite directions. A U-shaped ceramic permanent magnet encloses portions of a pole piece of one polarity while portions of the pole piece of the other polarity surround the outside surface of the U-shaped magnet. Energization of the coil in alternate directions causes the hammer module to move in successive increments.

[72] Inventors Alexander Nyman Dover; Robert H. Curtiss, Wayland, both of Mass.

[21] Appl. No. 835,998

[22] Filed June 24, 1969 [45] Patented Nov. 9, 1971 [73] Assignee Mohawk Data Sciences Corporation Hirkimer, NY.

[54] APPARATUS FOR PRODUCING INCREMENTAL MOVEMENT, PARTICULARLY FOR MOVING A PRINT HAMMER MODULE PARALLEL TO A PR MW, 4 14 Claims, 7 Drawing F lgs.

[52] u.s.c| 101/9312,

[51] Int. Cl l-l02k 41/02,

B4 1 j 9/04 [50] Field of Search 101/93 C. l11,93;310/12,l3,14,15,26,27;318/135,119, 121; 197/49, 50,51,58, 1

[56] Reierences Cited UNITED STATES PATENTS 1,986,639 1/1935 Konn 310/13 3,135,195 6/1964 Potter l01/93C 3,157,115 11/1964 Westetal 197/49X Primary Examiner-William B. Penn Anarneys- Francis .1. Thomas, Richard H. Smith, Thomas C. Siekman and Sughrue, Rothwell, Mion, Zinn and MacPeak Apparatus within a printer for incrementally moving a hammer module parallel to a line on which characters are being printed. The hammer module is carried across the paper by a coil which moves within a track extending parallel to the print line and formed by parts of pole pieces arranged to provide magnetic fields spaced along and extending across the track in alternating opposite directions. A U-shaped ceramic permanent magnet encloses portions of a pole piece of one polarity while portions of the pole piece of the other polarity surround the outside surface of the U-shaped magnet. Energization of the coil in alternate directions causes the hammer module to move in successive increments.

PATENTEI] NUV SIS?! 3,618,514

SHEET 1 OF 4 FIG. I

l I l I I8 "m $2 2 l8 1 I B 8q I Q I90) ZONE ZONE ZONE 20m; zomz l 2 3 4 5 FIG. 5

I NVENTORS ALEXANDER NYMAN ROB PATENTEDNUV 9l97l 3,618,514

SHEET 2 OF 4 PATENTEB NUV 91971 3,618,514

SHEET 3 or 4 APPARATUS FOR PRODUCING INCREMENTAL MOVEMENT. PARTICULARLY FOR MOVING A PRINT HAMMER MODULE PARALLEL TO A PRINT LINE BACKGROUND OF THE INVENTION This invention relates to an apparatus for producing incremental movement which may be utilized, for example, within a printer for incrementally moving a hammer module across the medium being printed upon.

Numerous printers have been developed to print the output information of data processing apparatus. Generally. in these printers one or more print hammers contained within a hammer module strike a printing medium (e.g. paper) and ribbon against type characters on a drum or chain revolving at high speed. The printing medium is successively advanced after each line is printed. Activation of the hammers is timed with respect to the drum or chain such that the desired type characters are impacted. Some printers contain hammer modules which move across the printing medium when printing a line. These contain fewer hammers than those printers having hammers arranged entirely across the printing medium. However. they are relatively complex and this complexity at least partially offsets the saving in hammer cost.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide a simple apparatus for producing incremental movement along a path which may be used to incrementally move a hammer module parallel to the print line.

It is another object to provide such an apparatus which is reliable, economical to operate and easy to repair.

It is a further object to provide such an apparatus having a detent means.

It is another object to provide a printer utilizing permanent magnets to move its hammer module parallel to the print line.

It is another object to provide a printer utilizing permanent magnets to move its hammer module with a minimal loss of magnetic flux.

It is a further object to provide a printer having a detent means for its movable hammer module.

In accordance with the invention, these and other objects are achieved by a coil projecting from the member to be incrementally moved, e.g.. a hammer module in a printer. Portions of the coil are adapted to be crossed by magnetic fields and move within a track. The magnetic fields are spaced along and extend across the track in alternating opposite directions so that by energizing the coil in alternate directions the coil is moved in successive increments. At least one ferromagnetic element rides within the track with the coil and, by being acted upon by the magnetic lines of force. brings the coil to a detent position after each increment.

The magnetic fields are generated by a permanent magnet and pole pieces. parts of which form the track within which the coil moves. The permanent magnet is U-shaped and encloses portions of the pole pieces of one polarity while portions of the pole pieces of the other polarity surround the outside surface of the U-shaped magnets.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view of a printer having a preferred embodiment of the invention for moving a hammer module.

FIG. 2 is a perspective view ofa typical portion of the means for generating the magnetic fields.

FIG. 3 is a view showing the coil attached to the hammer module.

FIG. 4 is a diagram illustrating the manner in which the hammer module is moved.

FIG. 4a is a diagram illustrating a modification of the apparatus shown in FIG. 4.

FIG. 5 is a schematic illustrating how the direction of travel ofthe hammer module is reversed.

FIG. 6 is a schematic block diagram of a control circuit for the printer.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 schematically illustrates a printer having a conventional print drum 1 with rows of type on its periphery and which is rotated by a driving means not shown. Paper 2 is advanced to a location adjacent the drum and across a line extending along the drum's length where printing occurs, i.e.. the print line. A pair of conventional tractors, 3 and 4, having toothed endless belts 5 which engage perforations in the paper move the paper an increment each time another line is to be printed. Each belt revolves around a pair of rollers. 7a and 7b. one of which is driven by a means not shown.

A hammer module 8 having four hammers 8a is positioned adjacent the drum at the print line. A connecting member 9. attached to the bottom of the hammer module 8. is movable along the drum's length and supported by a pair of guide members 10.

The apparatus for incrementally moving the hammer module along a line parallel to the print line is illustrated in FIGS. 1, 2 and 3. A coil 11, mounted on a plastic panel 12. is joined to the connecting member 9 and projects therefrom into a magnetic field-generating means. The magnetic fieldgenerating means, best shown in FIG. 2. is placed under the connecting member 9 and extends along the drum's length. It includes a U-shaped permanent ceramic magnet 13 constructed of any of the well-known ceramic magnetic materials. The magnet is a thin member magnetized through its thin dimension such that its opposite poles are on its opposed surfaces. A north pole piece I4 is located within and abuts the inside surface of the magnet 13. A U-shaped south pole piece 15 surrounds and abuts the outside surface of the magnet. Parts of both pole pieces project past the top of the magnet to form an air gap within which the coil I1 is located. Such a U-shaped arrangement keeps loss of magnetic flux to a minimum since the pole pieces abut substantially the entire poles of the magnet and the magnetic flux is concentrated at the airgap. During construction, the ceramic magnet may be formed by three mating parts: one part being the base of the U and the other two parts being the sides of the U.

At the top of the magnetic field-generating means. the pole pieces have spaced parts or projections which form the air gap and also a track within which the coil 11 moves. The projections 14a are located at the top of the north pole piece and form a comb arrangement having staggered teeth. The projections 15a of the south pole piece project into the spaces left vacant by the north pole piece projections I412. The projections thus form a track. each side of which has elements of opposite polarities alternatingly arranged. In addition. those elements directly opposing each other across the track are of opposite polarities. This arrangement provides magnetic fields crossing the track in alternating opposite directions.

FIG. 4 shows a section through the coil and illustrates the manner in which the hammer module is moved. The vertically extending portions Ila (shown in FIG. 3) of the coil 11 are placed between two adjacent pair of opposed pole piece projections. The coil 11 is thus crossed by two magnetic fields of opposite directions, each of which crosses one of the vertical portions llu. When the coil is energized. each vertical portion Ila of the coil develops a second magnetic field which interacts with the one within which it is located. However. energization of the coil II causes the two portions Ila to pass current in opposite vertical directions although both are perpendicular to the magnetic fields and. since the portions are crossed by opposite fields. each portion of the coil will have a force exerted upon it in the same direction and along the track.

By passing current in alternate directions through the coil via leads 16. shown in FIG. 3. the coil is made to move along the track in successive increments. Alternating the current as the coil moves along the track causes the proper directional force to be applied to each portion Ila of the coil for continuing its movement since the portions Ila of the coil move through opposite magnetic fields alternately arranged along the track. The coil is stepped along in this manner and carries the hammer module with it. The phantom lines in FIG. 4 illustrate the previous position of the left-hand vertical portion 11a. The pole piece projections are of such a size that the four hammers in the hammer module are positioned to print successive groups of four characters after each incremental movement of the hammer mechanism.

Of course, the relative size of the coil 11 and pole piece projections, 14a and a, may be varied without departing from the scope of the invention. For example, the vertical portions 110 of the coil may be located between every third pair of opposed pole piece extensions.

In order that the coil be properly positioned after each incremental movement, the panel 12 has attached thereto a pair of ferromagnetic elements 17. These elements provide a detent means for the apparatus. When current is stopped within the coil 11 at the end of an increment of movement by the module, the ferromagnetic elements 17 are located somewhere in the spaces between the pole piece projections 14a and 15a. However, they are then attracted by the magnetic forces from the pole piece projections to the edges of the projections nearest them and come to rest in the positions shown in FIG. 4. When the elements 17 are in these positions the vertical portions 11a of the coil 11 are properly positioned in the center between the pole piece projections for the next successive incremental movement. As also illustrated in FIG. 4, the ferromagnetic elements 17 preferably have pointed sides adjacent the pole piece projections to provide the most effective detent effect. Additionally, for more exact positioning of the coil, the edges of the pole piece projections toward which the ferromagnetic elements are attracted may be given a lipped configuration 17a pointing toward the track as shown in FIG. 4a. In such a case, the elements 17 will be attracted to and become positioned at the lips 170.

While the apparatus of the invention may be used to move the hammer modules in numerous printers, FIG. 5 schematically illustrates one possible arrangement having a print drum 1 and a hammer module 8 containing four hammers 8a. The module in the printer illustrated moves through five printing positions, zones 1-5. The printer is thus capable of printing up to characters in a line on the paper 2. Printing occurs when the module moves to the right. Upon reaching the right side of the paper, the module returns to the left-hand side to initiate another line. A pair of mechanical stops 18 are schematically illustrated at the ends of the printing drum 1. A momentary switch 19a is disposed at the left end of the drum and is closed as the module reaches the left end of the drum. Another momentary switch 19b is disposed at the right end of the drum and is closed as the module reaches the right end of the drum.

FIG. 6 illustrates one of many possible control circuits for the printer. A code disk 20, mounted on the shaft 1a of the rotating print drum 1, is interposed between a light source 21 and a photosensing device 22. The code disk has nine separate concentric bands. The innermost six bands 20a have 64 radial rows of transparent coded indicia, each row corresponding to one of 64 type characters on the drum. Six bands are required to produce 64 different binary-coded signals corresponding to the 64 characters on the drum. The next band 20b contains one timing indicia for each row in the inner bands 20a. The outermost band 200 has only one indicia and produces a signal on each cycle of the drum. The photosensing device 22 has nine separate detectors; six character detectors 22a, a timing detector 22b and a cycle detector 220, all of which cooperate with their respective bands on the disc. As each row of type characters approaches the hammers, the character detectors 22a of the photosensing device produce a unique binarycoded signal when energized by light passing through the coded indicia 20a of the disc. A series of pulses is produced by the timing detector 22b of the photosensing device, each pulse indicating one row of characters moving past the photosensing device. The pulses produced by the detector 220 of the photosensing device indicate each full drum cycle.

Cables 23a-d transmit coded input data to comparators 24a-d. The input data indicates the characters to be printed by the hammers 8a arranged along the print line at the drum. Each of the cables 23a-d contain six data lines, allowing for the binary-representation of 64 characters. The character indicating binary-coded signals from the photosensing device are also fed to the comparators over a common cable 25 and branch cables 25a. The common cable 25 and each of the branch cables 250 also contain six lines. Each comparator receives the data transmitted by one of the cables 23a-d and the data transmitted by the cable 25. When a match is indicated in a comparator, it supplies a pulse to a corresponding AND gate 26a-d.

Each of the AND gates 26a-d is opened upon receiving simultaneous signals from a control AND gate 27 and from a comparator. When opened, it provides a FIRE pulse to a hammer driver 28a-d. However, the control AND gate 27 only provides an output when receiving inputs over a line 29 from a flip-flop 30, from the timing detector 22b of the photosensing device, and over a line 31. The flip-flop 30 receives successive inputs from that detector 22c of the photosensing device which indicates the drum revolutions, and its outputs provide alternate pulses to either the control AND gate 27 or to a pulse generator 32 over a line 33. The pulse generator generates pulses for moving the module. Thus the flip-flop alternately provides a signal to the control AND gate 27 and allows hammer firing, or to the pulse generator 32 for moving the module.

The pulse generator 32 provides a pulse to another AND gate 34 which, when opened, allows a signal to reach flip-flop 35. The outputs of flip-flop 35 are alternately fed to negative and positive pulse generators 36a and 36b. These provide the necessary alternating current for the coil which moves the module, and energizes a hammer module control 37. Each pulse provided by either the positive or the negative pulse generator moves the module to a successive zone.

At the end of a printed line the module lies in zone 5 and must return to zone 1 to begin the next line. The next pulse fed to the module control when the module is in zone 5 attempts to move the module past the right end of the drum 1. However, one of the mechanical stops 18 prohibits further movement of the module to the right. Since the coil remains in the same magnetic field provided by the magnetic field-generating means, the next succeeding pulse, being of opposite polarity than the one preceding it, will cause the module to move to the left. The flip-flop 30 will continue to provide pulses to the pulse generator 32 and the module will travel leftward until it reaches zone 1. When in zone 1, the other stop 18 will provide the same effect and the module '5 direction of travel will again reverse. An on-ofi' switch 38 controls the modules movement via the AND gate 34. When the switch is opened the module control cannot receive any signals and the module is stopped. Upon closing the switch, the module will continue its movement in the same direction as before.

The on-off switch 38 controls the firing of the hammers 8a as well as on the module's movement. When initiating the printing operation, the switch 38 is closed causing the module to move and eventually close either of the two switches near the drums ends, depending on the modules direction of travel. Should the module travel to the right, the momentary switch 19b will be closed when the modules direction is reversed and a paper-advance signal fed over line 39 so that a new line may be printed when the module reaches zone 1. Should the module travel to the left, the paper will have already been advanced at the time that the module previously closed the momentary switch 19b in zone 5. In either case, when the module reaches zone 1 and closes the switch when reversing direction, an input pulse is provided to a ready flip-flop 40 which feeds a print signal over line 31 to the control AND gate 27 and thus allows energization of the hammer drivers 28a-d. After finishing a line, the module closes the switch 19b in zone 5 which is connected to the opposite terminal of the ready flip-flop 40 and terminates the print signal. This prevents firing of the hammer drivers while the module is returning to the left.

An OR gate 41 having its output connected to the ready flip-flop 40 prevents firing of the hammer drivers before the switch 19a is closed and the module is in a position to initiate a new line of print. The OR gate 41 receives one of its inputs from a pulse generator 42 controlled by the on-off switch 38 and, thus, the print signal is terminated by closing the on-off switch 38 as well as by the module closing switch 19b.

New data is requested by a signal over line 43 when an AND gate 44 is opened. The AND gate has two inputs: one is the print signal from the ready flip-flop 40 so that new data is requested only when the drivers are able to print; the other is a pulse from the pulse generator 32 such that new data is requested only during movement of the module to a successive zone.

A delay 45 is positioned between the pulse generator 32 and AND gate 44 to allow for a slight time lag required for the module to move to a successive zone.

Another delay 46 is positioned on line 39 to allow for the time lag required for the module to reverse its direction in zone 5. The period of delay occurring between energization of the photosensing device 22 and activation of the hammers 8a is compensated for by having the code disc lead the characters lb on the drum by an appropriate angle.

We claim:

1. Apparatus for producing incremental movement of a member along a predetermined path, the apparatus comprismg:

a. a track extending parallel to the predetermined path, the sides of the track containing elements spaced along the track and adapted to provide a plurality of magnetic fields spaced along and extending across the track in alternating directions;

b. an electrically energizable coil connected to the member and projecting therefrom, a portion of the coil being located within the track and adapted to pass current in a direction opposite to another portion of the coil within the track, the portions being adapted to be positioned with respect to the magnetic fields such that energizing the coil in alternate directions causes both portions to initiate successive increments of movement in one direction along the track; and

c. selectively operable circuit means for selectively energizing the coil in alternate directions.

2. The apparatus as recited in claim 1 wherein:

the elements for providing magnetic fields contained in each side of the track comprise pans of pole pieces, each side of the track containing spaced parts of alternating polarities, the parts directly opposing each other across the track, and the opposing parts being of opposite polarities;

and wherein:

each of the portions of the coil which are within the track and adapted to pass current in opposite directions is adapted to be positioned between the opposed parts of two adjacent pair of opposed pole piece parts;

and further including:

at least one permanent magnet for providing fiux to the pole pieces.

3. The apparatus as recited in claim 2 further comprising:

A. a panel on which the coil is mounted; and

B. at least one ferromagnetic element attached to the panel and located within the track, each ferromagnetic element being adapted to be positioned adjacent the edges of opposed pole piece parts, whereby each ferromagnetic element is attracted to a position adjacent said edges and a detent means for positioning the coil after each incremental movement is provided.

4. The apparatus as recited in claim 3 wherein the sides of the ferromagnetic elements adjacent the pole pieces are pointed.

5. The apparatus as recited in'claim 2 wherein opposite surfaces of the permanent magnet are of opposite polarities, and a portion of each of the pole pieces abuts a surface of the permanent magnet having the polarit of the ole piece.

6. The apparatus as recited in c arm 5 w erem the magnet is a thin member magnetized through its thin dimension.

7. The apparatus recited in claim 6 wherein the permanent magnet substantially surrounds a portion of one of the pole pieces of one polarity, and a portion of one of the pole pieces of the other polarity substantially surrounds the permanent magnet.

8. In a printer having a hammer module movable parallel to the print line, the improvement comprising:

a. a track extending parallel to the print line, the sides of the track containing elements spaced along the track and adapted to provide a plurality of magnetic fields spaced along and extending across the track in alternating directions;

b. an electrically energizable coil connected to the hammer module and projecting therefrom, a portion of the coil being located within the track and adapted to pass current in a direction opposite to another portion of the coil within the track, the portions being adapted to be positioned with respect to the magnetic fields such that energizing the coil in alternate directions causes both portions to initiate successive increments of movement in one direction along the track; and

c. selectively operable circuit means for selectively energizing the coil in alternate directions.

9. The printer as recited in claim 8 wherein:

the elements for providing magnetic fields contained in each side of the track comprise parts of pole pieces, each side of the track containing spaced parts of alternating polarities, the parts directly opposing each other across the track, and the opposing parts being of opposite polarities;

and wherein:

each of the portions of the coil which are within the track and adapted to pass current in opposite directions is adapted to be positioned between the opposed parts of two adjacent pair of opposed pole piece parts:

and further including:

at least one permanent magnet for providing fiux to the pole pieces.

10. The printer as recited in claim 9 further comprising:

a. a panel on which the coil is mounted; and

b. at least one ferromagnetic element attached to the panel and located within the track, each ferromagnetic element being adapted to be positioned adjacent the edges of opposed pole piece parts whereby each ferromagnetic element is attracted to a position adjacent said edges and a detent means for positioning the coil after each incremental movement is provided.

11. The apparatus as recited in claim 10 wherein the sides of the ferromagnetic elements adjacent the pole pieces are pointed.

12. The apparatus as recited in claim 9 wherein opposite surfaces of the permanent magnet are of opposite polarities, and a portion of each of the pole pieces abuts a surface of the permanent magnet having the polarity of said pole piece.

13. The apparatus as recited in claim 12 wherein the magnet is a thin member magnetized through its thin dimension.

14. The apparatus as recited in claim 13 wherein: the permanent magnet substantially surrounds a portion of one of the pole pieces of one polarity, and a portion of one of the pole pieces of the other polarity substantially surrounds the permanent magnet.

0 l I i l 

1. Apparatus for producing incremental movement of a member along a predetermined path, the apparatus comprising: a. a track extending parallel to the predetermined path, the sides of the track containing elements spaced along the track and adapted to provide a plurality of magnetic fields spaced along and extending across the track in alternating directions; b. an electrically energizable coil connected to the member and projecting therefrom, a portion of the coil being located within the track and adapted to pass current in a direction opposite to another portion of the coil within the track, the portions being adapted to be positioned with respect to the magnetic fields such that energizing the coil in alternate directions causes both portions to initiate successive increments of movement in one direction along the track; and c. selectively operable circuit means for selectively energizing the coil in alternate directions.
 2. The apparatus as recited in claim 1 wherein: the elements for providing magnetic fields contained in each side of the track comprise parts of pole pieces, each side of the track containing spaced parts of alternating polarities, the parts directly opposing each other across the track, and the opposing parts being of opposite polarities; and wherein: each of the portions of the coil which are within the track and adapted to pass current in opposite directions is adapted to be positioned between the opposed parts of two adjacent pair of opposed pole piece parts; and further including: at least one permanent magnet for providing flux to the pole pieces.
 3. The apparatus as recited in claim 2 further comprising: a. a panel on which the coil is mounted; and b. at least one ferromagnetic element attached to the panel and located within the track, each ferromagnetic element being adapted to be positioned adjacent the edges of opposed pole piece parts, whereby each ferromagnetic element is attracted to a position adjacent said edges and a detent means for positioning the coil after each incremental movement is provided.
 4. The apparatus as recited in claim 3 wherein the sides of the ferromagnetic elements adjacent the pole pieces are pointed.
 5. The apparatus as recited in claim 2 wherein opposite surfaces of the permanent magnet are of opposite polarities, and a portion of each of the pole pieces abuts a surface of the permanent magnet having the polarity of the pole piece.
 6. The apparatus as recited in claim 5 wherein the magnet is a thin member magnetized through its thin dimension.
 7. The apparatus recited in claim 6 wherein the permanent magnet substantially surrounds a portion of one of the pole pieces of one polarity, and a portion of one of the pole pieces of the other polarity substantially surrounds the permanent magnet.
 8. In a printer having a hammer module movable parallel to the print line, the improvement comprising: a. a track extending parallel to the print line, the sides of the track containing elements spaced along the track and adapted to provide a plurality of magnetic fields spaced along and extending across the track in alternating directions; b. an electrically energizable coil connected to the hammer module and projecting therefrom, a portion of the coil being located within the track and adapted to pass current in a direction opposite to another portion of the coil within the track, the portions being adapted to be positioned with respect to the magnetic fields such that energizing the coil in alternate directions causes both portions to initiate successive increments of movement in one direction along the track; and c. selectively operable circuit means for selectively energizing the coil in alternate directions.
 9. The printer as recited in claim 8 wherein: the elements for providing magnetic fields contained in each side of the track comprise parts of pole pieces, each side of the track containing spaced parts of alternating polarities, the parts directly opposing each other across the track, and the opposing parts being of opposite polarities; and wherein: each of the portions of the coil which are within the track and adapted to pass current in opposite directions is adapted to be positioned between the opposed parts of two adjacent pair of opposed pole piece parts; and further including: at least one permanent magnet for providing flux to the pole pieces.
 10. The printer as recited in claim 9 further comprising: a. a panel on which the coil is mounted; and b. at least one ferromagnetic element attached to the panel and located within the track, each ferromagnetic element being adapted to be positioned adjacent the edges of opposed pole piece parts whereby each ferromagnetic element is attracted to a position adjacent said edges and a detent means for positioning the coil after each incremental movement is provided.
 11. The apparatus as recited in claim 10 wherein the sides of the ferromagnetic elements adjacent the pole pieces are pointed.
 12. The apparatus as recited in claim 9 wherein opposite surfaces of the permanent magnet are of opposite polarities, and a portion of each of the pole pieces abuts a surface of the permanent magnet having the polarity of said pole piece.
 13. The apparatus as recited in claim 12 wherein the magnet is a thin member magnetized through its thin dimension.
 14. The apparatus as recited in claim 13 wherein: the permanent magnet substantially surrounds a portion of one of the pole pieces of one polarity, and a portion of one of the pole pieces of the other polarity substantially surrounds the permanent magnet. 